Healthy plant-based low-carb diets may benefit long-term weight management, study suggests

03 Jan 2024 --- Scientists are asserting that the source and quality of low-carbohydrate diets is crucial for weight management. New research links diets that emphasize high-quality protein, fat and carbohydrates from whole grains and other plant-based foods to lower weight gain.

Participants who increased their intake of total, animal-based and unhealthy low-carbohydrate diets gained more weight than those who increased their intake of healthy low-carb diets — focusing on plant-based proteins, healthy fats and fewer refined carbohydrates. 

The US-based researchers analyzed the diets and weights of 123,332 healthy adults between 1986 and 2018, with each participant providing self-reports on their diet and weight every four years. The study examines the associations between diets and weight change in over 20 years of follow-up. 

“The key takeaway here is that not all low-carbohydrate diets are created equal when it comes to managing weight in the long-term,” says senior author Qi Sun, associate professor in the department of nutrition at Harvard T.H. Chan School of Public Health, US. 

Healthy low-carb diets emphasize less refined carbohydrates, more plant protein and healthy fat. “Our findings could shake up the way we think about popular low-carbohydrate diets and suggest that public health initiatives should continue to promote dietary patterns that emphasize healthful foods like whole grains, fruits, vegetables and low-fat dairy products.”

Diet source and quality   
The study published in JAMA Network Open, shows data from three prospective cohort studies — the Nurses’ Health Study 1986-2010, Nurses’ Health Study II 1991-2015 and Health Professionals Follow-up Study 1986-2018. 

The authors scored the participants’ diets based on their adherence to five different categories of low-carbohydrate diets — total, animal-based, vegetable-based (emphasizing plant-based proteins and fats), healthy and unhealthy (emphasizing animal-based proteins, unhealthy fats and carbohydrates from unhealthy sources, such as processed bread and cereals). 

In their diet scores, the researchers distinguished between healthy carbs, such as non-starchy vegetables, fruits, legumes and whole grains, and less healthful carbohydrates, including those from potatoes, added sugar and refined grains. 

Healthy low-carbohydrate diets were linked to slower long-term weight gain, which the authors note is further evidence of the benefits of diets mostly composed of fruits, vegetables, healthy carbs (such as whole grains) and low-fat dairy products. 

“Our study goes beyond the simple question of, ‘To carb or not to carb?’” says lead author Binkai Liu, research assistant in the department of nutrition. “It dissects the low-carbohydrate diet and provides a nuanced look at how the composition of these diets can affect health over years, not just weeks or months.”

According to the authors: “The study findings argue against the sole focus of macronutrient quantity for weight management and suggest the crucial role of nutrient quality in maintaining a healthy body weight.”

The associations between healthy low-carbohydrate diets and lower weight gain were more pronounced among participants under 55, overweight, obese or less physically active. 

Low-carb diets   
The researchers note that low-carbohydrate diets have gained attention for their potential to promote weight loss and improve metabolic health. While clinical trials have linked these diets to favorable short-term weight changes, the study authors add that long-term weight management benefits remain unknown. 

They highlight that the study’s findings should be validated in more diverse populations to clarify the mechanisms underlying the identified associations. 

Moreover, results for the vegetable-based diet were less clear — in one study, they found a link between this diet and less weight gain over time, while results from the other studies were more mixed. 

Recently, researchers found additional health benefits for low-carbohydrate ketogenic diets, suggesting that these may protect against epileptic seizures in children through changes in the gut microbiome. 

Meanwhile, a research team in China found benefits of the keto diet in treating addiction and supporting overall health while warning that the strict nature of the diet may lead to an increased risk of malnutrition. 

By Jolanda van Hal